The present invention relates to injection valves for liquid chromatography. In particular, the present invention relates to sample injection apparatus for use with sample injection in injection valves that provides self-cleaning features.
A number of advances in high-performance liquid chromatography (HPLC) have reduced required sample volumes, reduced solvent and analyte consumption, improved sample resolution and reduced time and labor required for sampling. One aspect of HPLC testing which remains a problem is sample contamination in the system. In order for testing to be accurate and repeatable, extreme care must be taken to ensure that all parts of the sample equipment in contact with sample fluid are washed or flushed with solvents or wash fluids in order that all possible contamination is removed.
Current methods of sample flushing utilize cleaning the sample injection syringe to remove contaminates. The syringe then provides wash fluid by injection into the sample injection port of the HPLC injection valve. This process must be repeated until all measurable traces of contaminates are removed from the sample equipment.
Injection of wash or solvent fluid into the sample injection port is a time consuming evolution. The process must often be repeated since the volume of the syringe limits the amount of wash fluid injected during each evolution. Multiple injections of wash fluids increase the overall wash time corresponding to a decrease of throughput, and lead to premature wear-out of the movable parts involved.
An improved apparatus and method are needed to wash sample injection valves and associated equipment.
Therefore, an object of the present invention is to provide an apparatus which eliminates the requirement for an injection syringe or canula (probe) connected to a syringe in the sample injection port to wash the inlet portions of the HPLC injection valve.
Another object of the present invention is to provide a self-wash injection apparatus which utilizes separate reservoirs of wash fluids which are transferred by differential pressure to the injection valve of the equipment.
Another object of the present invention is to provide a self-washing injection apparatus for liquid chromatography injection valves that automatically seals the injection port from outside air to allow aspiration or pumping of the wash fluids into the injection valve.
Yet another object of the present invention is to provide a self-washing injection apparatus for liquid chromatography injection valves that reduces labor and the possibilities of errors in liquid chromatography testing.
The self-washing injection apparatus of the present invention attaches and seals to the inlet port of a sample injection valve used in liquid chromatography. The apparatus comprises a body enclosing an interior chamber. A penetrable seal such as a slit seal (duckbill seal) or a septum seal seals the top of the interior chamber. A sleeve seal engageable with an injection needle provides a fluid passageway at the bottom of the interior chamber to the injection port of the injection valve. The length of such a passageway can vary in order to allow positioning of the apparatus either immediately above the injection port of the injection valve or at a position separate from the injection valve. A wash port in the body of the device, connected to the interior chamber between the penetrable seal and the sleeve seal, provides a source of wash fluids during the washing cycle of the apparatus.
During sample injection, a sample injection needle passes through the penetrable seal and the interior chamber of the apparatus and seats in the sleeve seal below the interior chamber. A sealing surface on the ID of the sleeve seal seals the injection needle to the sleeve seal and provides a leak-tight fluid passageway to inject sample fluid into the sample injection valve.
Upon completion of sample introduction, the sample injection needle is removed and the sample injection valve is positioned to provide aspiration to the injection apparatus. The penetrable seal provides an air seal at the top of the interior chamber. The aspiration source draws wash fluids from one or more separate wash fluid reservoirs into the wash port of the apparatus, flushing the interior chamber, the sleeve seal, the injection port of the injection valve, and associated sample components of the sampling system. In other embodiments, a pressure source at the wash fluid reservoir provides the differential pressure to transfer wash fluid from the wash fluid reservoir to the injection port of the injection valve.
In the preferred embodiments, a threaded nipple on the bottom of the apparatus provides an attachment means to the injection port of the injection valve. A ferrule seal seals the apparatus to the injection valve. Multiple wash fluid inlet ports on the outside of the body of the apparatus connect to the interior chamber to simplify connection with one or more wash fluid reservoirs. In other embodiments, the apparatus is mounted remote from the injection valve and a tube connects the apparatus to the injection port of the injection valve.
The self-washing injection apparatus disclosed and claimed herein significantly simplifies washing of liquid chromatography sample components and reduces time and labor required for multiple samples.